Disk drives are widely used in computers, consumer electronics and data processing systems for storing information in digital form. The disk drive typically includes one or more storage disks and one or more head suspension assemblies. Each head suspension assembly includes a slider having an air bearing surface, and a read/write head that transfers information to and from the storage disk. The rotation of the storage disk causes the slider to ride on an air bearing so that the read/write head is at a distance from the storage disk that is referred to as a “head-to-disk spacing” (also sometimes referred to herein as a “flying height”).
Because today's disk drives utilize storage disks having increasingly high densities of data tracks, decreasing the head-to-disk spacing has become of great importance. However, this desire for a very small head-to-disk spacing must be balanced with tribological concerns in order to avoid damage to the read/write head and/or the storage disk, as well as loss of data. Thus, the range between head-to-disk contact and a desirable head-to-disk spacing has become extremely small, requiring an increasingly more accurate control system.
The difficulties of achieving a high degree of accuracy and reliability are further complicated by a phenomenon known as “seek loss”. As used herein, seek loss is a change in head-to-disk spacing that occurs as the read/write head moves radially in either direction over the storage disk, typically during a seek operation of the disk drive. Because the read/write head relies on rotation of the storage disk to create the air bearing, a change in velocity of the storage disk relative to the read/write head can cause a change in the head-to-disk spacing. The type of air bearing surface used as well as the velocity vectors of the read/write head relative to the storage disk can factor into changing the amount of support that the air bearing provides to the slider, even though the rotation rate of the storage disk may not be appreciably changing. Typically, this support changes during radial movement of the read/write head over the storage disk.
For example, with certain configurations of sliders, moving the slider toward the outer diameter can at least temporarily cause a decreased head-to-disk spacing, which can potentially result in undesirable head-to-disk contact. Conversely, moving the slider toward the inner diameter can at least temporarily cause too great of a head-to-disk spacing, making it more difficult to read servo track information during the seek process.